This invention relates to telecommunications switching and, in particular, to wireless switching systems.
A problem in the installing, provisioning, and deploying of in-building or campus personal communications systems (PCS) is the small physical size of the cells provided by the base stations. This is a problem because as an individual walks through a building with their wireless handset, the wireless handset is continuously re-registering on different base stations as it loses contacts with the previous base station. Such movements cause a large amount of traffic for the base stations as well as for the central controller that is providing overall control and switching for the wireless system. Since the central controller must be informed on which base station each wireless handset is registered, there is an advantage in the central controller knowing the exact base station on which a wireless handset is registered. When an incoming call is received for the handset, the wireless system controller can immediately set up the call via the base station to the wireless handset. If the wireless system controller simply knows that the wireless handset is registered on one of the base stations in the wireless system, then, the wireless system controller must attempt to set up the incoming call via all the base stations.
Within the prior art these problems have been resolved by the utilization of logical coverage areas. Base stations are grouped into logical coverage areas, and the wireless system controller is only informed that a wireless handset is registered on a base station within a particular logical coverage area. When an incoming call is received for the wireless handset, the wireless system controller only attempts to establish a connection to the wireless handset through the base stations that make up the logical coverage area of the wireless handset. Within a logical coverage area, if a wireless handset moves from one base station to another, the wireless handset does not re-register on the other base station since it is in the same logical coverage area. This greatly reduces the number of re-registrations and assists in the amount of work that must be done to route incoming calls to a wireless handset.
Logical coverage areas are used in many wireless protocols such as PHS, DECT, or PWT. However, problems do exist with the utilization of logical coverage areas. First, the use of logical coverage areas complicates the provisioning and deploying of new PCS wireless networks since a great deal of time and effort must be spent in determining which base stations should be placed in which logical coverage areas. Further, within a building or a campus, people do not move in constant and uniform patterns. Rather, people enter the wireless system in the morning and leave in the evening. People go to a cafeteria for lunch, or go to an auditorium for a large meeting. The result is that no matter how carefully the provisioning and deployment of the logical coverage areas is performed, a static deployed logical coverage areas are not efficient for all conditions in most installations.
The foregoing problems are solved, and a technical advance is achieved, by an apparatus and method that dynamically rearrange logical coverage areas to meet the traffic needs of a wireless switching system. Once the logical coverage areas are established, the logical coverage areas adapt to the changing needs of the community of wireless handsets. Advantageously, in a first embodiment, the adaptation is controlled by individual base stations, or in a second embodiment, the adaptation is controlled by a system wireless controller that controls the wireless switching system.
In the first embodiment, a base station in a first logical coverage area determines when it should join a second logical coverage area by monitoring the frequency of registrations of wireless handsets from all other logical coverage areas. When registrations from the second logical coverage area exceed a predetermined threshold rate, the base station joins the second logical coverage area. To join the second logical coverage area, the base station requests permission from another base station within the second logical coverage area. If the number of base stations in the second logical coverage area does not exceed a predetermined threshold number, the other base station gives the base station permission to join the second logical coverage area.
In the second embodiment, the system wireless controller maintains a frequency table for each base station. The frequency table records the rate of registrations from other logical coverage areas to the base station. When registrations from a second logical coverage area to a base station in a first logical coverage area exceed a predetermined threshold rate, the system wireless controller transfers the base station from the first logical coverage area to second logical coverage area if the number of base stations already in the second logical coverage area does not exceed a predetermined threshold.